Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other modulation techniques. A CDMA system provides certain advantages over other types of systems, including increased system capacity.
A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “C.S0002-A Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 cdma2000 High Rate Packet Data Air Interface Specification” (the cdma2000 standard), (4) the “TIA/EIA-IS-856 CDMA2000 High Rate Packet Data Air Interface Specification” (the IS-856 standard), and (5) some other standards.
Cellular communication system users commonly have a service agreement with a cellular provider. The system operated by a cellular provider may cover a limited geographical area. When a user travels outside of this geographical area, service may be provided by another system operator, under a roaming agreement. There is often more than one service provider in a particular region, so a user may have a choice as to which service provider to roam with. As cellular communication systems have proliferated, networks of cellular systems have been organized under common service providers, or with contractual agreements between service providers. Roaming fees are minimized or eliminated when a user transfers between systems which are party to such agreements. As such, modern mobile stations often make use of Preferred Roaming Lists (PRLs), which contain information about the preferred systems for roaming and various parameters needed for communication therewith. PRLs may be pre-programmed in a mobile station when service is initiated. Alternatively, PRLs can be programmed with over-the-air data transfers. Such programming is described in “TIA/EIA-683-B Over-the-Air Service Provisioning of Mobile Stations in Spread Spectrum Systems”, a standard compatible with the above named wireless communication systems.
The list of sectors in a typical PRL can be quite large, and will likely grow larger as more mobile stations are equipped for international roaming. Furthermore, in data communication systems, such as the HDR standard, each sector is assigned an IPv6 (Internet Protocol version 6) address which is 128 bits in length. As the length of the PRL increases, and as the information in each record in the PRL expands, the memory requirements to store the PRL will grow accordingly. Furthermore, over-the-air updates to the PRL will take longer as the PRL size expands. There is therefore a need in the art for efficient storage and retrieval of Preferred Roaming Lists.